1. Field of the Invention
The invention relates to the control of fluid flow into a wellbore. More particularly, the invention relates to a flow control apparatus that is self adjusting to meter production and choke the flow of gas into the wellbore.
2. Description of the Related Art
In hydrocarbon wells, horizontal wellbores are formed at a predetermined depth to more completely and effectively reach formations bearing oil or other hydrocarbons in the earth. Typically, a vertical wellbore is formed from the surface of a well and thereafter, using some means of directional drilling like a diverter, the wellbore is extended along a horizontal path. Because the hydrocarbon bearing formations can be hundreds of feet across, these horizontal wellbores are sometimes equipped with long sections of screened tubing which consists of tubing having apertures therethough and covered with screened walls, leaving the interior of the tubing open to the inflow of filtered oil.
Horizontal wellbores are often formed to intersect narrow oil bearing formations that might have water and gas bearing formations nearby. FIG. 1 illustrates two such nearby formations, one of water and one of gas. Even with exact drilling techniques, the migration of gas and water towards the oil formation and the wellbore is inevitable due to pressure drops caused by the collection and travel of fluid in the wellbore. Typically, operators do not want to collect gas or water along with oil from the same horizontal wellbore. The gas and water must be separated at the surface and once the flow of gas begins it typically increases to a point where further production of oil is not cost effective. Devices have been developed that self adjust to control the flow of fluid into a horizontal wellbore. One such device is shown in U.S. Pat. No. 6,371,210 owned by the same assignee as the present invention and that patent is incorporated by reference in its entirety herein. The '210 patent teaches a self-adjusting device that chokes the flow of fluid into a horizontal wellbore as the flow of fluid increases relative to a preset value determined by a spring member. Multiple devices can be placed along the length of a wellbore to help balance the inflow of production throughout the length of the wellbore. The device includes a piston that is depressed by a force generated by fluid flow. The device is especially useful when several are used in series along the length of a horizontal wellbore. However, the devices are not designed to meter production while choking unwanted production components due to its lack of a constantly sized orifice though which to meter the flow of production and determine the relative amounts of gas or water.
There is a need therefore, for a self-adjusting flow control apparatus for downhole use in a wellbore that operates to limit the inflow of gas or water into the wellbore when that component in a production stream reaches a predetermined percentage relative to the oil. There is a further need, for a flow control apparatus for use in a wellbore that is self-regulating and self-adjusts for changes in the amount of fluid and gas in a production stream. There is yet a further need for a flow control apparatus that meters the flow of production into a horizontal wellbore.